DESCRIPTION: (Investigator's Abstract) The project proposes to use the anterior eye (cornea and conjunctiva) and its sensory innervation as an assay of irritancy and toxic effects. The anterior eye has unique characteristics: extensive use in toxicology, permeability, relative ease of observation, and importance to the input of visual information. In addition, the eye is unique in that receptors innervating the cornea differ from those innervating conjunctiva, and hence comparisons of these populations will likely be useful to assay for deficits in performance of difference types of sensory neurons. The personnel of Topical Testing have expertise in recording from corneal sensory neurons in vivo, in growing (and recording from) neural tissue in vitro, and in the design and fabrication of specialized equipment used in such studies. This Phase I feasibility study will investigate the adaptation of a new technology, which may allow monitoring of activity on a number of neurons simultaneously, and hence may improve the commercial productivity of Topical Testing's methods for estimating the ocular irritancy potential of chemical substances.